Recently, it is remarkable in increasing the definition of pictures due to an increase in the resolution of a digital camera and the like and increasing the capacity of a data storage device such as an SD™ card and achieving high picture quality by increasing the frame rate of picture data. Based on the above background, a transmission amount of data between the host device such as a digital camera or the like and a memory device or the like that records data continues to increase. In transmitting such a large amount of data, a high-speed serial transmission system based on a small amplitude differential signal is generally used from the viewpoint of simplifying connection cables, suppressing the power consumption and reducing EMI radiation noise. Further, in the above high-speed serial transmission system, it is general to use coding of 8b/10b in order to stabilize the transmission.
If the same data items (such as “00” or “FF”) are successively transmitted at the data communication time by use of the serial transmission system, harmonic noise with a frequency component corresponding to a period of the successive patterns. Therefore, as a method for coping with the above case, a so-called scramble system that superimposes a random number on the data and transmits the result is known. For example, the system is disclosed in “High-Speed Serdes Devices and Applications”, by David Robert Stauffer et. al., published by Springer, 2008, pp. 140 to 143.
However, in the conventional scramble system, a method for coping with a case wherein fixed patterns are successively transmitted in order to maintain synchronization of serial transmission at the data non-transmission time, that is, in an idle state is not taken into consideration and a problem that noise occurs in the idle state is not yet solved.